Stormwater chamber with stackable reinforcing ribs

ABSTRACT

An arch-shaped corrugated chamber having corrugation peaks and valleys, with reinforcing ribs provided on the corrugation peaks. The ribs extend upwardly from a chamber base to a rib upper end, and have an arch-shaped cross-section with an outer surface extending outwardly from a corrugation peak and a fin extending inwardly from the corrugation peak, and optionally, a rib line provided on the rib outer surface centered on the rib arch-shaped cross-section. A channel formed by the inner surface of the rib is sized to receive a corresponding rib of a second chamber so that multiple similar chambers with ribs may be stacked together.

FIELD OF THE INVENTION

This application relates generally to molded plastic chambers for waterdetention and, more particularly to open bottomed, arch-shaped moldedplastic chambers that are buried in the ground and receive stormwaterrunoff from paved and roofed areas for storage and release into thelocal water table to replenish groundwater supply.

BACKGROUND OF THE INVENTION

Stormwater runoff collected from roof areas and paved areas werehistorically directed into municipal stormwater drainage systems andreleased into a local body of water. However, regulatory changes andgood practice now mandate that stormwater runoff must be collected anddirected to local soil where it can replenish groundwater supplies.

The traditional construction of stormwater handling systems has beenconcrete tanks or infiltration trenches filled with large gravel orcrushed stone with perforated pipes running therethrough. Such stonefilled trench systems are non-economical and/or inefficient since thestone occupies a substantial volume, limiting the ability of the systemto handle large surge volumes associated with heavy storms. Both thestone and the perforated pipe are also susceptible to clogging byparticles or debris carried by water.

Molded plastic chamber structures were introduced to the market to takethe place of concrete structures for handling stormwater. U.S. Pat. No.5,087,151 to Robert J. DiTullio, the disclosure of which is herebyincorporated by reference, is an early patent in the field whichdiscloses a drainage and leaching field system comprising vacuum-moldedpolyethylene chambers that are designed to be connected and lockedtogether in an end-to-end fashion to provide a water handling system.

Stormwater chambers typically have a corrugated arch-shapedcross-section and are relatively long with open bottoms for dispersingwater to the ground. The chambers are typically buried within crushedstone aggregate or other water permeable granular medium that typicallyhas 20-40 percent or more void space. The chambers serve as waterreservoirs in a system that includes both the chambers and surroundingcrushed stone. The crushed stone is located beneath, around, and abovethe chambers and acts in combination with the chambers to provide pathsfor water to percolate into the soil, and also provides a surroundingstructure that bears the load of any overlying materials and vehicles.The chambers will usually be laid on a crushed stone bed side-by-side inparallel rows, then covered with additional crushed stone to createlarge drainage systems. End portions of the chambers may be connected toa catch basin, typically through a pipe network, in order to efficientlydistribute high velocity stormwater. Examples of such systems areillustrated in U.S. Pat. Nos. 7,226,241 and 8,425,148 to Robert J.DiTullio, the disclosures of which are also incorporated by reference.

The use of molded plastic chamber structures has grown substantiallysince their initial introduction to the market, and have replaced theuse of concrete structures in many applications. Molded plastic chamberstructures provide a number of distinct advantages over traditionalconcrete tanks or stone-filled trench systems. For example, concretetanks are extremely heavy requiring heavy construction equipment to putthem in place. Stone-filled trench systems are expensive and inefficientsince the stone occupies a substantial volume, limiting the ability ofthe system to handle large surge volumes of water associated with heavystorms.

More recently, manufacturers have begun to offer taller chambers whichoffer larger volume and storage capacity. Examples of recentlyintroduced large capacity chambers include the Cultec® 902HD®, Contech®Chambermaxx®, Stormtech® MC-3500 and 4500, Prinsco® HS180, and LaneSK180.

A design consideration associated with larger size stormwater chambersis that such structures may experience greater load stress than smallerchambers. A chamber should have a load bearing strength capable ofbearing the load of the overlaying crushed stone and paving, and loadscorresponding to use of construction equipment and vehicular trafficover the location of the buried chamber. Therefore, use ofsub-corrugations molded into the corrugations to improve the strength oflarger size plastic stormwater chambers has been proposed. U.S. Pat. No.8,491,224 describes a chamber for stormwater runoff with sub-corrugationfeatures on corrugation peaks and/or corrugation valleys. U.S. Pat. No.8,672,583 similarly describes a plastic stormwater chamber withsub-corrugations that run along peak corrugations or valleycorrugations. U.S. Pat. No. 8,672,583 defines sub-corrugations as“smaller or secondary corrugations which are superimposed on thecorrugations.” (U.S. Pat. No. 8,672,583 at Col. 3, lines 26-27; see alsoCol. 6, lines 53-57).

A commercially acceptable product is required to fit on a standard sizepallet and to be stackable such that a commercially acceptable quantityof product can be shipped on each pallet. Typically, a pallet may notexceed 40×48 inches in size and/or 84 inches in height, although theexact size is determined by each carrier. Although shipping costs aretypically based on weight, many carriers also offer a per-pallet pricingwhere the shipper pays fixed amount per pallet no matter what thefreight commodity or the freight class. It is commercially desirable tofit as much product on a pallet as possible, in order to minimizeshipping costs. Thus products are designed in order to be fitted on andshipped with the maximum quantity of product on a pallet. In the case ofplastic stormwater chambers this means that desirably six or more largesize chambers can fit on a pallet so that the value of product shippedis commercially proportionate to the shipping cost. A plastic stormwaterstorage chamber designed so that four or less large size chambers fit ona pallet would not provide a value of product shipped that iscommercially proportionate to the shipping cost.

Identically-formed chambers with corrugations can be readily stacked asthey nest together one on top of the other sufficiently closely that thequantity of product on a pallet is commercially acceptable. Chamberswith sub-corrugations on the corrugations nest together and can bestacked in a way that permits a commercially acceptable quantity ofproduct to be loaded on a pallet. But chambers that do not nest togetherwill not permit packing a sufficient number of chambers on a pallet.

One example of chambers that have heretofore been considered undesirablebecause of the inability to nest them together for packing arestormwater chambers with reinforcing ribs or fins instead ofsubcorrugations. Ribs and fins are relatively narrow plastic structuresused for strengthening. A properly-sized rib or fin can provide greaterstrengthening effect and stiffness relative to a sub-corrugation.However, the increase in strength provided has heretofore been at theloss in commercial acceptability in packaging, particularly with respectto larger size chambers. The use of reinforcing ribs or fins or otherincreases in wall thickness prevents the chambers from nesting togetherin a stack. The stacking and other problems associated with use of ribsor fins is well recognized in the art. (See e.g. U.S. Pat. No. 8,672,583at Col. 2, lines 6-12, and 46-52, and Col. 4, lines 4-9.) As such, ribsand fins are generally considered by persons of ordinary skill in theart to be a distinctly different feature than a sub-corrugation. Seee.g. U.S. Pat. No. 8,672,583 at col. 6, lines 64-67.

Therefore, there continues to be a need in the stormwater managementfield for larger size chambers that have strengthening elements thathave both the strength of ribbing, and the stackability ofsub-corrugations. The desired chamber would be both stronger thanexisting design approaches, and also be adapted for efficient and costeffective distribution and transportation of such chambers.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide astormwater chamber with reinforcing ribs. It is a further object of thepresent invention to provide such a stormwater chamber that is readilystackable for transport and storage. It is a further object to provide amethod of manufacturing such a stormwater chamber.

These and other objectives are achieved by providing a plasticarch-shaped corrugated chamber having a plurality of corrugation peaksand a plurality of corrugation valleys, with reinforcing ribs providedon the corrugation peaks. The ribs extend upwardly from a chamber baseto a rib upper end. The ribs have an arch-shaped cross-section whichextends outwardly from a corrugation peak and a fin which extendsinwardly from a center of the arch-shaped cross-section. The arch-shapedcross-section has a depth, and the fin has a depth which is less thanthe depth of the arch-shaped cross-section. A rib line is provided onthe rib outer surface centered on the rib arch-shaped cross-section andaligned with the fin.

The arch-shaped cross-section and the fin define a channel. The channelis sized to receive a corresponding rib of a second chamber so thatmultiple similar chambers with reinforcing ribs may be stacked together.Preferably, the rib extends upwardly from the chamber base to a ribupper end, and the rib arch-shaped cross-section depth and fin depthtaper from a greater depth adjacent to the chamber base to a lesserdepth adjacent to the rib upper end such that the channel has a varyingdepth ranging from a maximum depth adjacent the base to a minimum depthadjacent a location above the base.

Preferably, the rib has a vertical height which is between 30% to 80% ofa vertical height of the chamber, and more preferably between 40% to 60%of the vertical height of the chamber.

The chamber may be formed of a molded plastic sheet, or by injectionmolding, but most preferably is a cellular plastic material.

Other objects of the present invention are achieved by provision of amethod of manufacturing a chamber, comprising steps of: providing apolymer melt; injecting a CO2 blowing agent into the polymer melt;injecting the polymer melt and CO2 blowing agent into a mold cavity, themold cavity defining a plastic arch-shaped corrugated chamber having aplurality of corrugation peaks and a plurality of corrugation valleysdistributed along a length of the chamber, the corrugation peaks andvalleys having a thickness, the corrugation peaks and corrugationvalleys extending transverse to a lengthwise axis of the chamber, thechamber having a top portion and two side portions, with a base at alower end of each side portion, and a rib provided on a plurality of theplurality of corrugation peaks, each rib having an arch-shapedcross-section with an outer surface extending outwardly from acorrugation peak and a fin extending inwardly from the corrugation peak.

Other objects of the invention and its particular features andadvantages will become more apparent from consideration of the followingdrawings and accompanying detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front, top and left side perspective view of a chamberaccording to an exemplary embodiment of the present invention.

FIG. 2 is a left side elevation view of the stormwater chamber shown inFIG. 1.

FIG. 3 is a top plan view of the stormwater chamber shown in FIG. 1.

FIG. 4 is a bottom plan view of the stormwater chamber shown in FIG. 1.

FIG. 5 is a front elevation view of the stormwater chamber shown in FIG.1.

FIG. 6 is a partial sectional view of the stormwater chamber at thesection 6-6 shown in FIG. 2.

FIG. 7 is a detail bottom plan view of the bottom of a stormwaterchamber, at the location 7 shown in FIG. 4, illustrating a rib.

FIG. 8 is a detail bottom view of FIG. 7 illustrating the rib.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a plastic stormwater chamber 10 according to anexemplary embodiment of the present invention. The chamber 10 has agenerally arch-shaped cross-section defined by two sidewalls 12, 14,running the length of the chamber 10 between a first end and a secondend, and a top wall 16 there between. The first sidewall 12 has a base18 a and the second sidewall 14 has a base 18 b.

The plastic arch-shaped chamber 10 is corrugated and has a plurality ofcorrugation peaks 20 and a plurality of corrugation valleys 22distributed along a length of the chamber. The corrugation peaks 20 andcorrugation valleys 22 extend transverse to a lengthwise axis of thechamber 10. The corrugation peaks 20 and valleys 22 have a thicknesswhich is generally uniform and reflects the thickness of the materialwhich is used to form chamber 10. In one embodiment of the invention,the material thickness is 0.375 inch. The corrugation peaks 20 andvalleys 22 act as circumferential reinforcing members to providestrength and rigidity to the chamber 10. In preferred embodiments, thechamber 10 has a smaller corrugation 24 at one end and a largercorrugation 26 at the other end, whereby the larger corrugation 26 canoverlap the smaller corrugation 24 to connect the chambers together, asdescribed in U.S. Pat. No. 5,087,151.

In accordance with the invention, reinforcing ribs 30 are provided onone or more of the corrugation peaks 20. Preferably, the ribs 30 areprovided on all corrugation peaks 20 except for the corrugations 24 and26 at each end of the chamber. Ribs 30 extend upwardly from the chamberbases 18 a, 18 b to a rib upper end 31. The rib has a vertical height asillustrated in FIG. 6 as the vertical distance between the plane of thebase 18 b and the line A-A. The rib vertical height is between 30% to80% of a vertical height of the chamber, and optionally may be between40% to 60% of the vertical height of the chamber. In one embodiment,each of the ribs 30 rises to a height that is less than half the heightof the chamber 10.

Ribs 30 have an arch-shaped cross-section 40 as seen in FIGS. 7 and 8.The arch-shaped cross-section 40 extends outwardly from a corrugationpeak 20 from locations 35. A fin 36 extends inwardly from a center 42 ofthe arch-shaped cross-section 40. Fin 36 extends perpendicularly to thesurface of the arch-shaped cross-section 40 from the inner wall of therib 30. Fin 36 has a depth which is less than the depth of the ribarch-shaped cross-section 40. Preferably, fin 36 has a width whichtapers from center 42 of the arch-shaped cross-section 40 to fin end 37.A rib line 44 is provided on the rib 30 outer surface centered on therib arch-shaped cross-section 40 and aligned with the fin 36.

In one embodiment, chamber 10 has a material thickness of 0.375 inch.Fin 36 has a width of 0.30 inch tapering to 0.25 inch at fin end 37, anda depth of 0.625 inch at bases 18 a, 18 b tapering to 0.1 inch at ribupper end 31 where it tapers into the surface of corrugation peak 20.Rib line 44 has a width of 0.30 inch and a depth of 0.17 inch which alsotapers into the surface of corrugation peak 20. Accordingly, thethickness of corrugation peak 20 in the area of rib 30 across the widthof the rib 30 changes greatly due to the additional thickness providedby the depth of fin 36 and the rib line 44. The total thickness of thecorrugation peak 20 in the area of rib 30 may be 1.17 inch, which issubstantially greater than the 0.375 inch thickness of thickness ofcorrugation peak 20.

Referring now to FIGS. 3, 4, 7, and 8, as seen therein, arch-shapedcross-section 40 of rib 30 preferably is a curved cross-sectional shapeand the exterior surface 32 thereof is curved and arch-shaped. A curvedcross-sectional shape is preferred, but optionally the exterior surface32 of the ribs 30 may have different shapes and/or cross-sections suchas triangular, rectangular, or tapered with flat distal ends.

The shape of the arch-shaped cross-section 40 and fin 36 define achannel 34. Channel 34 has a depth which is the difference between theinner wall 38 of crest corrugation 20 and the fin end 37 which is theinner surface of fin 36. Channel 34 has a depth varying from maximumdepth adjacent the base 18 a, 18 b to a minimum depth adjacent alocation above the base 18 a, 18 b. In one embodiment, the channel 34minimum depth is located at the rib upper end 31.

For example, as seen in FIG. 8, the arch-shaped cross-section 40 and fin36 may have a depth (D₁) as measured between the outer wall 46 of thearch-shaped cross-section 40 and the fin end 37 of fin 36 ofapproximately one (1) inch at the base. The overall depth (D₂) betweenthe outer wall 46 of the arch-shaped cross-section 40 and the inner wall38 of the peak corrugation 20 may be 1.375 inches. In such case, thechannel 34 will have a depth of 0.375 inches at the base.

The rib 30 and its arch-shaped cross-section 40 decrease in size fromthe base 18 a, 18 b to the rib upper end 31. In a preferred embodimentas seen in FIG. 2, the width of each rib 30 decreases between the base18 a, 18 b and the rib upper end 31. The width of rib 30 at the base 18is greater than its width at rib upper end 31. In this embodiment eachof the corrugation peaks 20 also has a width that decreases between thebase 18 a, 18 b and the rib upper end 31. In addition to a decreasingwidth, the rib 30 and its arch-shaped cross-section 40, and fin 36decrease in depth from the base 18 a, 18 b to the rib upper end 31.Consequently, channel 34 also decreases in depth from the base 18 a, 18b to the rib upper end 31.

The channel 34 is sized to receive a corresponding rib 30 of a secondchamber so that multiple similar chambers with reinforcing ribs 30 maybe stacked together. The design of rib 30 with channel 34 permitsstacking the chambers 30 which still maintaining the strength of aribbed structure. A rib 30 of a lower stacked chamber 10 can nestagainst and at least partially into the channel 34 of an upper stackedchamber 10.

Ribs 30, featuring the combination of the arch-shaped cross-section 40and the fin 36 have significantly strength modulus compared tocorrugations or sub-corrugations with uniform wall thicknesses

Although ribs 30 are shown on the exterior of the corrugation peaks 20,the ribs 30 may alternatively be on the interior of the corrugationpeaks 20, or in some embodiments, on the corrugation valleys 22 betweenthe corrugation peaks 20.

Chamber 10 optionally includes valley subcorrugations 50 on thecorrugation valleys 22. Valley subcorrugations 50 extend across the topwall 16 and downwardly along part of the two sidewalls 12, 14.Preferably, the valley subcorrugations 50 extend downwardly sufficientlythat the lower ends 52 of valley subcorrugations 50 are located belowthe rib upper ends 31. The overlapping of the ribs 30 and valleysubcorrugations 50 provides stronger sidewalls 12, 14 because there isno unreinforced zone in an area of potential load stress.

Chamber 10 may be formed of a molded plastic sheet, or by injectionmolding, but most preferably is a cellular plastic material. A method ofmanufacturing a chamber 10, comprises the steps of: providing a polymermelt which can be a single polymer or a copolymer blend; then injectinga CO2 blowing agent into the polymer melt; and injecting the polymermelt and CO2 blowing agent into a mold cavity. The mold cavity definesthe plastic arch-shaped corrugated chamber 10 having a plurality ofcorrugation peaks 20 and a plurality of corrugation valleys 22distributed along a length of the chamber 10, and ribs 30 provided on aplurality of the plurality of corrugation peaks, as previouslydescribed.

In one embodiment of the invention, chamber 10 has an axial length of1.25 meters, a width of 1.981 meters, and a height of 1.219 meters, andprovides a storage volume for collected water of 1.84 m³/unit.

Although the invention has been described with reference to a particulararrangement of parts, features and the like, these are not intended toexhaust all possible arrangements or features, and indeed manymodifications and variations will be ascertainable to those of skill inthe art.

What is claimed is:
 1. A method of manufacturing a stormwater chamber,comprising steps of: providing a polymer melt; injecting a CO2 blowingagent into the polymer melt; and injecting the polymer melt and CO2blowing agent blend into a mold cavity to form a cellular plastic foamchamber, the formed chamber being an arch-shaped corrugated chamberhaving a plurality of corrugation peaks and a plurality of corrugationvalleys distributed along a length of the chamber, the corrugation peaksand corrugation valleys extending transverse to a lengthwise axis of thechamber, the chamber having a top portion and two side portions, with abase at a lower end of each side portion, and a rib provided on aplurality of the plurality of corrugation peaks, each rib having anarch-shaped cross-section with an outer surface extending outwardly froma corrugation peak and a fin extending inwardly from the corrugationpeak, wherein each rib extends upwardly from one of the bases to a ribupper end, the rib having a depth and the fin having a depth, the ribdepth and the fin depth tapering from a greater depth adjacent to theone of the bases to a lesser depth above the one of the bases such thatthe rib and the fin define a channel sized to receive a correspondingrib of a second chamber, the channel having a depth varying from amaximum depth adjacent the one of the bases to a minimum depth adjacenta location above the one of the bases.
 2. The method of claim 1, whereineach rib has the arch-shaped cross-section extending outwardly with thefin centered on and extending inwardly from the rib arch-shapedcross-section.
 3. The method of claim 2, wherein the rib arch-shapedcross-section has a depth and the fin depth is less than the depth ofthe rib arch-shaped cross-section.
 4. The method of claim 1, wherein therib has a vertical height which is 30% to 80% of a vertical height ofthe chamber.
 5. The method of claim 4, wherein the rib vertical heightis 40% to 60% of the vertical height of the chamber.
 6. The method ofclaim 1, wherein the channel minimum depth is located at the rib upperend.
 7. The method of claim 3, wherein the rib arch-shaped cross-sectiondecreases in size from one of the bases to the rib upper end.
 8. Themethod of claim 1, wherein the arch-shaped cross-section wall thicknessis 0.375 inch and the depth of the fin is 0.625 inch at the locationadjacent to the one of the bases.
 9. The method of claim 1, wherein thedepth of the fin is 0.625 inch and the depth of the arch-shapedcross-section between the outer wall of the arch-shaped cross-sectionand an inner wall of a corrugation peak is 1.375 inch at the locationadjacent to the one of the bases.
 10. A method of manufacturing astormwater chamber, comprising steps of: providing a polymer melt;injecting a CO2 blowing agent into the polymer melt; and injecting thepolymer melt and CO2 blowing agent blend into a mold cavity to form acellular plastic foam chamber, the formed chamber being an arch-shapedcorrugated chamber having a plurality of corrugation peaks and aplurality of corrugation valleys distributed along a length of thechamber, the corrugation peaks and valleys having a thickness, thecorrugation peaks and corrugation valleys extending transverse to alengthwise axis of the chamber, the chamber having a top portion and twoside portions, with a base at a lower end of each side portion, and arib provided on a plurality of the plurality of corrugation peaks, eachrib having an arch-shaped cross-section extending outwardly from acorrugation peak and having an outer wall, each rib further having a finextending inwardly from a center of the rib arch-shaped cross-section,each rib extending upwardly from one of the bases to a rib upper end,the rib arch-shaped cross-section having a wall thickness and a depth,and the fin having a depth, the fin depth being greater than thearch-shaped cross-section wall thickness at a location adjacent to theone of the bases, the rib arch-shaped cross-section depth and the findepth tapering from a greater depth adjacent to the one of the bases toa lesser depth above the one of the bases, whereby the rib arch-shapedcross-section and the fin define a channel sized to receive acorresponding rib of a second chamber, the channel having a depthvarying from a maximum depth adjacent the one of the bases to a minimumdepth adjacent a location above the one of the bases.
 11. The method ofclaim 10, wherein the fin depth is less than the depth of the ribarch-shaped cross-section.
 12. The method of claim 10, wherein the ribhas a vertical height which is 30% to 80% of a vertical height of thechamber.
 13. The method claim 12, wherein the rib vertical height is 40%to 60% of the vertical height of the chamber.
 14. The method of claim10, wherein the rib arch-shaped cross-section decreases in size from oneof the bases to the rib upper end.
 15. The method of claim 10, whereinthe arch-shaped cross-section wall thickness is 0.375 inch and the depthof the fin is 0.625 inch at the location adjacent to the one of thebases, and the depth of the arch-shaped cross-section between the outerwall of the arch-shaped cross-section and an inner wall of a corrugationpeak is 1.375 inch at the location adjacent to the one of the bases. 16.A method of manufacturing a stormwater chamber, comprising steps of:injecting a polymer melt into a mold cavity to form a cellular plasticfoam chamber, the formed chamber being an arch-shaped corrugated chamberhaving a plurality of corrugation peaks and a plurality of corrugationvalleys distributed along a length of the chamber, the corrugation peaksand corrugation valleys extending transverse to a lengthwise axis of thechamber, the chamber having a top portion and two side portions, with abase at a lower end of each side portion, and a rib provided on aplurality of the plurality of corrugation peaks, each rib having anarch-shaped cross-section with an outer surface extending outwardly froma corrugation peak and a fin extending inwardly from the corrugationpeak, wherein each rib extends upwardly from one of the bases to a ribupper end, the rib having a depth and the fin having a depth, the ribdepth and the fin depth tapering from a greater depth adjacent to theone of the bases to a lesser depth above the one of the bases such thatthe rib and the fin define a channel sized to receive a correspondingrib of a second chamber, the channel having a depth varying from amaximum depth adjacent the one of the bases to a minimum depth adjacenta location above the one of the bases.
 17. The method of claim 16,wherein each rib has the arch-shaped cross-section extending outwardlywith the fin centered on and extending inwardly from the rib arch-shapedcross-section.
 18. The method of claim 16, wherein the rib arch-shapedcross-section has a depth and the fin depth is less than the depth ofthe rib arch-shaped cross-section.
 19. The method of claim 16, whereinthe rib has a vertical height which is 30% to 80% of a vertical heightof the chamber.
 20. The method of claim 19, wherein the rib verticalheight is 40% to 60% of the vertical height of the chamber.
 21. Themethod of claim 16, wherein the channel minimum depth is located at therib upper end.
 22. The method of claim 16, wherein the rib arch-shapedcross-section decreases in size from one of the bases to the rib upperend.